Heat pump and cascaded caloric regenerator assembly

ABSTRACT

A heat pump, as provided herein, may include a hot side heat exchanger, a cold side heat exchanger, a pump, and a caloric heat pump. The caloric heat pump may include a regenerator housing, a plurality of stages, and a field generator. The regenerator housing may extend along an axial direction between a first end portion of the regenerator housing and a second end portion of the regenerator housing. The plurality of stages may be arranged sequentially along the axial direction from the first end portion to the second end portion. The plurality of stages may be arranged so that caloric temperature peaks of the plurality of stages increase along the axial direction according to a predetermined, non-linear curve. The field generator may be positioned adjacent to the plurality of stages to subject the plurality of stages to a variable field generated by the field generator.

FIELD OF THE INVENTION

The present subject matter relates generally to heat pumps, such as magneto-caloric heat pumps, for appliances.

BACKGROUND OF THE INVENTION

Conventional refrigeration technology typically utilizes a heat pump that relies on compression and expansion of a fluid refrigerant to receive and reject heat in a cyclic manner so as to effect a desired temperature change or transfer heat energy from one location to another. This cycle can be used to receive heat from a refrigeration compartment and reject such heat to the environment or a location that is external to the compartment. Other applications include air conditioning of residential or commercial structures. A variety of different fluid refrigerants have been developed that can be used with the heat pump in such systems.

While improvements have been made to such heat pump systems that rely on the compression of fluid refrigerant, at best such can still only operate at about forty-five percent or less of the maximum theoretical Carnot cycle efficiency. Also, some fluid refrigerants have been discontinued due to environmental concerns. The range of ambient temperatures over which certain refrigerant-based systems can operate may be impractical for certain locations. Other challenges with heat pumps that use a fluid refrigerant exist as well.

Magneto-caloric materials (MCMs) (i.e., materials that exhibit the magneto-caloric effect) provide a potential alternative to fluid refrigerants for heat pump applications. In general, the magnetic moments of MCMs become more ordered under an increasing, externally applied magnetic field and cause the MCMs to generate heat. Conversely, decreasing the externally applied magnetic field allows the magnetic moments of the MCMs to become more disordered and allow the MCMs to absorb heat. Some MCMs exhibit the opposite behavior (i.e., generating heat when the magnetic field is removed)—such MCMs are sometimes referred to as para-magneto-caloric material, but both types are referred to collectively herein as magneto-caloric material or MCM. The theoretical Carnot cycle efficiency of a refrigeration cycle based on an MCMs can be significantly higher than for a comparable refrigeration cycle based on a fluid refrigerant. As such, a heat pump system that can effectively use an MCM would be useful.

Challenges exist to the practical and cost competitive use of an MCM, however. In addition to the development of suitable MCMs, equipment that can attractively utilize an MCM is still needed. Currently-proposed equipment may require relatively large and expensive magnets, may be impractical (e.g., for use in appliance refrigeration), and may not otherwise operate with enough efficiency to justify capital cost.

Accordingly, a heat pump system that can address certain challenges, such as those identified above, would be useful. Such a heat pump system that can also be used in a refrigerator appliance would also be useful.

BRIEF DESCRIPTION OF THE INVENTION

Aspects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention.

In one exemplary aspect of the present disclosure, a heat pump is provided. The heat pump may include a hot side heat exchanger, a cold side heat exchanger, a pump, and a caloric heat pump. The pump may be operable to flow a working fluid between the hot and cold side heat exchangers. The caloric heat pump may include a regenerator housing, a plurality of stages, and a field generator. The regenerator housing may extend along an axial direction between a first end portion of the regenerator housing and a second end portion of the regenerator housing. The regenerator housing may define a chamber that extends longitudinally along the axial direction between the first and second end portions of the regenerator housing. The plurality of stages may be positioned within the regenerator housing. The plurality of stages may be arranged sequentially along the axial direction from the first end portion to the second end portion. Each stage of the plurality of stages may include a caloric material having a caloric temperature peak. The plurality of stages may be arranged so that the caloric temperature peaks of the plurality of stages increase along the axial direction according to a predetermined, non-linear curve. The field generator may be positioned adjacent to the plurality of stages to subject the plurality of stages to a variable field generated by the field generator.

In another exemplary aspect of the present disclosure, a refrigerator appliance is provided. The refrigerator appliance may include a cabinet defining a chilled chamber; and a heat pump system operable to cool the chilled chamber. The heat pump system may include a hot side heat exchanger, a cold side heat exchanger, a pump, and a caloric heat pump. The pump may be operable to flow a working fluid between the hot and cold side heat exchangers. The caloric heat pump may include a regenerator housing, a plurality of stages, and a field generator. The regenerator housing may extend along an axial direction between a first end portion of the regenerator housing and a second end portion of the regenerator housing. The regenerator housing may define a chamber that extends longitudinally along the axial direction between the first and second end portions of the regenerator housing. The plurality of stages may be positioned within the regenerator housing. The plurality of stages may be arranged sequentially along the axial direction from the first end portion to the second end portion. Each stage of the plurality of stages may include a caloric material having a caloric temperature peak. The plurality of stages may be arranged so that the caloric temperature peaks of the plurality of stages increase along the axial direction according to a predetermined, non-linear curve. The field generator may be positioned adjacent to the plurality of stages to subject the plurality of stages to a variable field generated by the field generator.

These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures.

FIG. 1 provides a perspective view of a refrigerator appliance according to exemplary embodiments of the present disclosure.

FIG. 2 provides a schematic view of certain components of a heat pump system positioned in the exemplary refrigerator appliance of FIG. 1.

FIG. 3 provides a perspective view of a heat pump according to exemplary embodiments of the present disclosure.

FIG. 4 provides an exploded perspective view of the exemplary heat pump of FIG. 3.

FIG. 5 provides a cross-sectional view of the exemplary heat pump of FIG. 3.

FIG. 6 provides a front perspective view of the exemplary heat pump of FIG. 3.

FIG. 7 provides a schematic representation of various steps in the use of a stage of the exemplary heat pump of FIG. 3.

FIG. 8 provides a chart of change in energy over temperature, illustrating caloric temperature ranges for several exemplary stages of caloric material as further described below.

FIG. 9 provides a chart of caloric temperature peak over a normalized longitudinal position (e.g., an axial direction), illustrating multiple non-linear curves for several exemplary stages of caloric material as further described below.

DETAILED DESCRIPTION

Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents.

As used herein, the term “or” is generally intended to be inclusive (i.e., “A or B” is intended to mean “A or B or both”). The terms “first,” “second,” and “third” may be used interchangeably to distinguish one component from another and are not intended to signify location or importance of the individual components.

The present subject matter may be utilized in a caloric heat pump system for heating or cooling an appliance, such as a refrigerator appliance. While described in greater detail below in the context of a magneto-caloric heat pump system, one of skill in the art using the teachings herein will recognize that other suitable caloric materials may be used in a similar manner to heat or cool an appliance (i.e., apply a field, move heat, remove the field, move heat). For example, electro-caloric material heats up and cools down within increasing and decreasing electric fields. As another example, elasto-caloric material heats up and cools down when exposed to increasing and decreasing mechanical strain. As yet another example, baro-caloric material heats up and cools down when exposed to increasing and decreasing pressure. Such materials and other similar caloric materials may be used in place of or in addition to the magneto-caloric material described below to heat or cool liquid/water within an appliance. Thus, caloric material is used broadly herein to encompass materials that undergo heating or cooling when exposed to a changing or variable field from a field generator, where the field generator may be a magnet, an electric field generator, an actuator for applying mechanical stress or pressure, etc.

Referring now to FIG. 1, an exemplary embodiment of a refrigerator appliance 10 is depicted as an upright refrigerator having a cabinet or casing 12 that defines a number of internal storage compartments or chilled chambers. In particular, refrigerator appliance 10 includes upper fresh-food compartments 14 having doors 16 and lower freezer compartment 18 having upper drawer 20 and lower drawer 22. Drawers 20, 22 are “pull-out” type drawers in that they can be manually moved into and out of freezer compartment 18 on suitable slide mechanisms. Refrigerator 10 is provided by way of example only. Other configurations for a refrigerator appliance may be used as well including appliances with only freezer compartments, only chilled compartments, or other combinations thereof different from that shown in FIG. 1. In addition, the heat pump and heat pump system of the present disclosure is not limited to refrigerator appliances and may be used in other applications as well (e.g., air-conditioning, electronics cooling devices, etc.). Thus, it should be understood that while the use of a heat pump and heat pump system to provide cooling within a refrigerator is provided by way of example herein, the present disclosure may also be used to provide for heating applications as well.

FIG. 2 is a schematic view of various components of refrigerator appliance 10, including a refrigeration compartment 30 and a machinery compartment 40. Refrigeration compartment 30 and machinery compartment 40 include a heat pump system 52 having a first or cold side heat exchanger 32 positioned in refrigeration compartment 30 for the removal of heat therefrom. A heat transfer fluid such as, for example, an aqueous solution, flowing within first heat exchanger 32 receives heat from refrigeration compartment 30 thereby cooling contents of refrigeration compartment 30. A fan 38 may be used to provide for a flow of air across first heat exchanger 32 to improve the rate of heat transfer from refrigeration compartment 30.

The heat transfer fluid flows out of first heat exchanger 32 by line 44 to heat pump 100. As will be further described herein, the heat transfer fluid receives additional heat from caloric material in heat pump 100 and carries this heat by line 48 to pump 42 and then to second or hot side heat exchanger 34. Heat is released to the environment, machinery compartment 40, or other location external to refrigeration compartment 30 using second heat exchanger 34. A fan 36 may be used to create a flow of air across second heat exchanger 34 and thereby improve the rate of heat transfer to the environment. Pump 42 connected into line 48 causes the heat transfer fluid to recirculate in heat pump system 52. Motor 28 may be in mechanical communication with heat pump 100, as described below.

From second heat exchanger 34, the heat transfer fluid returns by line 50 to heat pump 100 where, as will be further described below, the heat transfer fluid loses heat to the caloric material in heat pump 100. The now colder heat transfer fluid flows by line 46 to first heat exchanger 32 to receive heat from refrigeration compartment 30 and repeat the cycle as just described.

Heat pump system 52 is provided by way of example only. Other configurations of heat pump system 52 may be used as well. For example, lines 44, 46, 48, and 50 provide fluid communication between the various components of heat pump system 52 but other heat transfer fluid recirculation loops with different lines and connections may also be employed. For example, pump 42 can also be positioned at other locations or on other lines in system 52. Still other configurations of heat pump system 52 may be used as well.

FIGS. 3 through 6 depict various views of an example heat pump 100 of the present invention. Heat pump 100 includes a regenerator housing 102 that extends longitudinally along an axial direction between a first end portion 118 and a second end portion 120. The axial direction is defined by axis A-A about which regenerator housing 102 rotates. A radial direction R is defined by a radius extending orthogonally from the axis of rotation A-A (FIG. 5). A circumferential direction is indicated by arrows C.

Regenerator housing 102 defines one or more chambers 104 that extends longitudinally along the axial direction defined by axis A-A. For example, chamber 104 may extend along the axial direction defined by axis A-A between first and second end portions 118, 120 of regenerator housing 102. Chamber 104 may also extend along circumferential direction C about the axis A-A. Alternatively, multiple chambers 104 may be position proximate or adjacent to each other along circumferential direction C. Chamber 104 includes a pair of openings 106, 108 positioned at opposing end portions 118, 120 of regenerator housing 102.

Heat pump 100 also includes a working unit 112 that include caloric material. Working unit 112 is located in a chamber 104 and extends along the axial direction A-A (e.g., between first and second end portions 118, 120 of regenerator housing 102).

In certain embodiments, working unit 112 also extends along circumferential direction C about the axis A-A. Thus, working unit 112 may have a cylindrical shape that is complementary to or fills chamber 104. In particular, working unit 112 may have a cylindrical inner surface 130 and a cylindrical outer surface 132 that are spaced along the radial direction R. Working unit 112 may be a single, unitary piece of caloric material in certain example embodiments. Thus, regenerator housing 102 may not include baffles or walls that separate the working unit 112 into sections.

In alternative embodiments, working unit 112 is provided as a plurality of discrete, fluidly-isolated segments that each include a caloric material. Each segment of such working unit 112 may be located in a separate chamber 104 and extend along axial direction A-A. Thus, two or more segments of working unit 112 may be positioned adjacent to each other along the circumferential direction C and extend longitudinally along the axial direction A-A.

Regenerator housing 102 defines a cavity 128 that is positioned radially inward of the chamber 104 and extends along the axial direction between first and second end portions 118, 120 of regenerator housing 102. A field generator 126 (e.g., a magnet, an electric field generator, an actuator for applying mechanical stress or pressure, etc.) is positioned within cavity 128 and, for this example embodiment, extends along the axial direction between first end 118 and second end portion 120. Field generator 126 provides a variable field (e.g., a magnetic field, an electrical field, a mechanical strain field, a pressure field, etc.) that is directed radially outward as indicated by arrows M in FIG. 5. In exemplary embodiments, field generator 126 may be configured as an electromagnet or a combination of an electromagnet and one or more magnets—each of which can be configured to generate a magnetic field (e.g., having a constant or variable magnetic flux along the axial direction A-A).

The positioning and configuration of field generator 126 is such that only a portion of working unit 112 (or a subset of the plurality of segments) is within field M at any one time. For example, as shown in FIG. 5, about half of working unit 112 is within the field M while the remainder of working unit 112 is positioned remote from or outside of the field M created by field generator 126. However, as regenerator housing 102 is continuously rotated along the circumferential direction as shown by arrow W, the portion of working unit 112 within the field M will continuously change as some of working unit 112 will enter field M and another portion of working unit 112 will exit the field M.

A pair of valves or seals 136, 138 is provided such that the seals 136, 138 are positioned in an opposing manner at the first and second end portions 118, 120 of regenerator housing 102. More particularly, a first seal 136 is positioned at first end portion 118 and a second seal 138 is positioned at second end 120. First seal 136 has a first inlet port 140 and a first outlet port 142. The ports 140, 142 of first seal 136 are positioned adjacent to opening 106 of chamber 104. As shown, ports 140, 142 are positioned one hundred eighty (180) degrees apart about the circumferential direction C of first seal 136. However, other configurations may be used. For example, ports 140, 142 may be positioned within a range of about one hundred seventy (170) degrees to about one hundred ninety (190) degrees about the circumferential direction C as well.

Second seal 138 has a second inlet port 144 and a second outlet port 146. The ports 144, 146 of second seal 138 are positioned adjacent to opening 108 of chamber 104. As shown, ports 144, 146 are positioned one hundred eighty (180) degrees apart about the circumferential direction C of second seal 138. However, other configurations may be used. For example, ports 144, 146 may be positioned within a range of about one hundred seventy (170) degrees to about one hundred ninety (190) degrees about the circumferential direction C as well. Ports 144, 146 are connected with lines 50, 48 (FIG. 1), respectively. As such, the rotation of regenerator housing 102 about axis A-A sequentially places lines 48, 50 in fluid communication with the channels within the caloric material of working unit 112 as will be further described. Notably, at any one time during rotation of regenerator housing 102, lines 46, 50 may each be in fluid communication with at least channel 150 within the caloric material of working unit 112 while lines 44, 48 may also be in fluid communication with at least one other channel 150 within the caloric material of working unit 112 about one hundred eighty (180) degrees away along the circumferential direction.

A heat transfer fluid may flow into chamber 104 through inlet ports 140, 144 of seals 136, 138 so as to flow through the caloric material in working unit 112 and then exit through outlet ports 142, 146 of seals 136, 138. A reverse path can be used for flow of the heat transfer fluid in the opposite direction through the working unit 112. Seals 136, 138 may be positioned relative to regenerator housing 102 such that working fluid flows through channels 150 within working unit 112 when aligned with ports of seals 136, 138. Tight clearances between seals 136, 138 and working unit 112 may allow working fluid flow to only pass through channels 150 adjacent or aligned with ports 140 through 146. Regenerator housing 102 may be rotatable relative to first and second seal 136, 138. Ports 140, 142 are connected with lines 44, 46 (FIG. 1), respectively. As such, the rotation of regenerator housing 102 about axis A-A sequentially places lines 44, 46 in fluid communication with channels within the caloric material of working unit 112 as will be further described.

FIG. 7 illustrates an exemplary method of the present disclosure using a schematic representation of a portion of working unit 112 of caloric material in regenerator housing 102 as it rotates in the direction of arrow W between positions 1 through 8 as shown in FIG. 6. During step 200, the portion of working unit 112 is fully within field M, which causes the moments of the material to orient and the caloric material to heat as part of the caloric effect. Ordering of the field is created and maintained as the portion of working unit 112 is rotated sequentially through positions 2, 3, and then 4 (FIG. 6) as regenerator housing 102 is rotated in the direction of arrow W. During the time at positions 2, 3, and 4, the heat transfer fluid dwells in the caloric material of the portion of working unit 112 and, therefore, is heated.

In step 202, as regenerator housing 102 continues to rotate in the direction of arrow W, the portion of working unit 112 will eventually reach position 5 (FIG. 6). As shown in FIGS. 3 and 6, at position 5 the heat transfer fluid can flow through the material as inlet port 140 in first seal 136 is aligned with the channels 150 within the portion of working unit 112 while outlet port 146 in second seal 138 at the second end portion 120 is also aligned with the channels 150 within the portion of working unit 112. As indicated by arrow Q_(H-OUT), heat transfer fluid in the portion of working unit 112, now heated by the caloric material, can travel out of regenerator housing 102 and along line 48 to the second heat exchanger 34 (FIG. 2). At the same time, and as indicated by arrow Q_(H-IN), heat transfer fluid from first heat exchanger 32 (FIG. 2) flows into the portion of working unit 112 from line 44 when working unit 112 is at position 5. Because heat transfer fluid from the first heat exchanger 32 is relatively cooler than the caloric material in working unit 112, the caloric material will lose heat to the heat transfer fluid.

Referring again to FIG. 7 and step 204, as regenerator housing 102 continues to rotate in the direction of arrow W, the portion of working unit 112 is moved sequentially through positions 6, 7, and 8 (FIG. 6) where the portion of working unit 112 is completely or substantially out of field M. The absence or lessening of the field M is such that the moments of the material become disordered and the caloric material absorbs heat as part of the caloric effect. During the time in positions 6, 7, and 8, the heat transfer fluid dwells in the caloric material of the portion of working unit 112 and, therefore, is cooled by losing heat to the caloric material as the moments disorder. More specifically, the heat transfer fluid does not flow through working unit 112 because the openings 106, 108, 122, and 124 corresponding to working unit 112 when in positions 6, 7, and 8 are not aligned with any of the ports 140, 142, 144, or 146.

Referring to step 206 of FIG. 7, as regenerator housing 102 continues to rotate in the direction of arrow W, the portion of working unit 112 will eventually reach position 1 (FIG. 6). As shown in FIGS. 3 and 6, at position 1 the heat transfer fluid in the portion of working unit 112 can flow through the material as inlet port 144 in second seal 138 is aligned with the channels 150 within the portion of working unit 112 while outlet port 142 in first seal 136 is also aligned with the channels 150 within the portion of working unit 112. As indicated by arrow Q_(C-OUT), heat transfer fluid in the portion of working unit 112, now cooled by the caloric material, can travel out of regenerator housing 102 and along line 46 to the first heat exchanger 32 (FIG. 2). At the same time, and as indicated by arrow Q_(C-IN), heat transfer fluid from second heat exchanger 34 (FIG. 2) flows into the portion of working unit 112 from line 50 when the portion of working unit 112 is at position 5. Because heat transfer fluid from the second heat exchanger 34 is relatively warmer than the caloric material in the portion of working unit 112 at position 5, the caloric material will lose some of its heat to the heat transfer fluid. The heat transfer fluid now travels along line 46 to the first heat exchanger 32 to receive heat and cool the refrigeration compartment 30 (FIG. 2).

As regenerator housing 102 is rotated continuously, the above described process of placing each portion of working unit 112 in and out of field M is repeated. Additionally, the size of field M and regenerator housing 102 are such that one portion of working unit 112 may be within the field M at any given time during rotation. Similarly, the remainder of the working unit 112 may be outside (or substantially outside) of the field M at any given time during rotation. Additionally, at any given time, there may be only a portion of working unit 112 through which the heat transfer fluid is flowing while the remainder of working unit 112 remains in a dwell mode. More specifically, while one portion of working unit 112 is losing heat through the flow of heat transfer fluid at position 5, another portion of working unit 112 is receiving heat from the flowing heat transfer fluid at position 1, while all remaining portions of working unit 112 are in dwell mode. As such, the system can be operated continuously to provide a continuous recirculation of heat transfer fluid in heat pump system 52 as working unit 112 rotates through positions 1 through 8.

As will be understood by one of skill in the art using the teachings disclosed herein, the number of ports in seals 136, 138 or other parameters can be varied to provide different configurations of heat pump 100 while still providing for continuous operation. For example, each valve could be provided within two inlet ports and two outlet ports so that heat transfer fluid flows through at least four portions of working unit 112 at any particular point in time. Alternatively, regenerator housing 102 or seals 136, 138 could be constructed so that, for example, at least two portions of working unit 112 are in fluid communication with an inlet port and outlet port at any one time. Other configurations may be used as well.

Accordingly, as shown in FIG. 7, each working unit 112 can be provided with stages 152, 154, 156, 158, 160, and 162 of different caloric materials that are arranged sequentially along a predetermined direction (e.g., along axial direction A-A in this exemplary embodiment). Each such stage includes a caloric material that exhibits the caloric effect at a different temperature or a different temperature range than an adjacent stage along the axial direction A-A. The range of temperature over which the caloric material (normal or inverse) in each stage exhibits the desired caloric response to provide heating or cooling is referred to herein as the “caloric temperature range.” In the case of a magneto-caloric material, this may also be referenced as the “Curie temperature range.” The temperature at which the caloric material in each stage exhibits its maximum caloric effect (i.e., peak change in energy) is referred to herein as the “caloric temperature peak.” In the case of a magneto-caloric material, this may also be referenced as the “Curie temperature peak.”

The stages (e.g., 152, 154, 156, 158, 160, and 162) can be arranged to that the caloric temperature ranges (e.g., Curie temperature ranges) of the plurality of stages increases along a predetermined direction such as axial direction A-A (FIG. 3). For example, stage 152 may exhibit the magnet caloric effect at a temperature less than the temperature at which stage 154 exhibits the magnet caloric effect, which may be less than such temperature for stage 156, and so on. By configuring the appropriate number and sequence of stages of caloric material (e.g., MCM), heat pump 100 can be operated over a substantial range of ambient temperatures.

A motor 28 (FIG. 2) is in mechanical communication with regenerator housing 102 (FIG. 3) and provides for rotation of housing 102 about axis A-A. By way of example, motor 28 may be connected directly with housing 102 by a shaft or indirectly through a gear box. Other configurations may be used as well.

In exemplary embodiments, the caloric temperature ranges of stages (e.g., 152, 154, 156, 158, 160, and 162) are selected to overlap in order to facilitate heat transfer.

Such an overlap is illustrated in FIG. 8, which provides a chart of change in energy over temperature for several exemplary stages of caloric material (e.g., C8-1, C8-2, C8-3, C8-4, C8-5, C8-6, C8-7, C8-8, C8-9, and C8-10). Specifically, FIG. 8 provides a plot of the amount of temperature change (ΔT) (e.g., in units of Kelvin) for stages of different caloric materials as a function of operating temperature T (e.g., in units of Kelvin). Similar to the arrangement of FIG. 7, each sequential stage (e.g., C8-1 through C8-10) is longitudinally sequential (e.g., along the axial direction A-A). For example, C8-1 may represent an initial stage, such as 152 (FIG. 7), while C8-3 represents a longitudinally-adjacent stage, such as 154 (FIG. 7). Moreover, C8-4 may represent a further stage, such as 156 (FIG. 7) that is longitudinally-adjacent to C8-3, and so on. As shown, the caloric temperature range (e.g., Curie temperature range) for one stage (e.g., C8-1 through C8-10) may overlap or coincide with at least a portion of the caloric temperature range for the stage(s) that is/are adjacent to that one stage (e.g., adjacent along the axial direction A-A—FIG. 3).

At stated, different types or alloys of caloric materials can have different caloric temperature ranges over which the caloric material will substantially exhibit a caloric effect (e.g., magneto-caloric effect). In addition, the caloric temperature peak can also be different for different caloric materials. In exemplary embodiments, such as those shown in FIG. 8, the caloric temperature peaks may increase sequentially (e.g., along the axial direction A-A—FIG. 3).

Turning especially to FIG. 9, a chart is provided illustrating exemplary caloric temperature peaks (e.g., in units Kelvin), such as Curie temperature peaks, defined by the adjacent stages of caloric material along the axial direction A-A (FIG. 3) (e.g., as a relative scale of normalized longitudinal position between 0 and 1). Specifically, two discrete embodiments are illustrated at C9-1 and C9-2, respectively. Each curve C9-1 and C9-2 represents a plot of a discrete set of stages of caloric material that are arranged sequentially (e.g., as shown with stages 152-162 in FIG. 7). Thus, C9-1 represents a separate embodiment/configuration from C9-2. In the exemplary plotted embodiments, the horizontal axis (i.e., Normalized Longitudinal Position) represents the working unit 112 (FIG. 3) along the axial direction A-A, which is evenly distributed from the first end portion (i.e., 0 in the horizontal axis of Normalized Longitudinal Position) to the second end portion (i.e., 1 in the horizontal axis Normalized Longitudinal Position). Each plotted point on C9-1 and C9-2 indicates a caloric temperature peak for a discrete stage of caloric material. In other words, each dot may represent a unique stage of caloric material located at the normalized longitudinal position. Thus, T_(o) on FIG. 9 indicates a value of caloric temperature peak at the first end portion 118 (FIG. 3), and T₁ indicates a value of caloric temperature peak at the second end portion 120 (FIG. 3).

As shown, a plurality of stages of the regenerator 112 (FIG. 3) may be arranged so that the caloric temperature peaks of the plurality of stages increase along the axial direction A. When assembled, the stages (i.e., the plotted peaks of each stage) form a predetermined, non-linear curve (e.g., C9-1 or C9-2) along the axial direction. Thus, the overall increase in caloric temperature peaks for the stages may be non-linear.

In optional embodiments, the non-linear curve (e.g., C9-1 or C9-2) may exclusively increase. Thus, each subsequent stage may have a caloric material that defines a caloric temperature peak that is equal to or greater than the caloric material of the previous stage (e.g., from 0 to 1 along the normalized longitudinal position or axial direction A-A).

In certain embodiments, the non-linear curve (e.g., C9-1 or C9-2) is primarily controlled or set according to the selection of caloric materials between adjacent stages. In some such embodiments, each stage of the plurality of axial stages defines a common axial length. In other words, the length of each stage of caloric material may be equal in length along the axial direction A-A (FIG. 3) (e.g., perpendicular to the field generator 126). For instance, using FIG. 7 as a reference, each axial length L1, L2, L3, L4, L5, and L6 may be equal to each other. Thus, in order for the adjacent stages 152 through 162 to form a non-linear curve (e.g., C9-1 or C9-2—FIG. 9) caloric materials of each stage (e.g., 152, 154, 156, 158, 160, 162) will be varied accordingly.

In alternative embodiments, the non-linear curve (e.g., C9-1 or C9-2) is further controlled or set according to a variation in axial length between one or more of the plurality of stages. One or more stages of the plurality of stages may thus define a discrete axial length that is unique from an axial length defined by another stage of the plurality of stages. In other words, the length of at least one stage of caloric material along the axial direction A-A may be different or unique from the length of another stage of caloric material. For instance, using FIG. 7 as a reference, one or more of the axial lengths L1, L2, L3, L4, L5, or L6 may be different from another axial length L1, L2, L3, L4, L5, or L6. Thus, in order for the adjacent stages 152 through 162 to form a non-linear curve (e.g., C9-1 or C9-2—FIG. 9) axial length (e.g., L1, L2, L3, L4, L5, or L6), as well as the caloric material, of each stage (e.g., 152, 154, 156, 158, 160, 162) will be varied accordingly.

As illustrated in FIG. 9, the non-linear curve (e.g., C9-1 or C9-2) generally defines a curvature ratio (Cr) across the axial direction A-A. For example, the non-linear curve (e.g., C9-1 or C9-2) may be represented as a polynomial equation, such as

T=Ax+Bx ²   Eq. 1

wherein

T is the caloric temperature peak value;

x is the normalized longitudinal position value;

A=B−T_(max)−T_(min); and

B=C_(r)/(1−C_(r))* T_(max)

In the exemplary embodiments C9-1 and C9-2 of FIG. 9, T_(max) equal T₁, while T_(min) equals T_(o). Thus, the curvature ratio C_(r) may a non-zero value that is either positive (as in the case of C9-1) or negative (as in the case of C9-2). The absolute value of the curvature ratio C_(r) may be greater than zero and less than one (i.e., 0<|C_(r)|<1). In certain embodiments, the curvature ratio C_(r) is a non-zero value between −0.5 and 0.5. In additional or alternative embodiments, the curvature ratio C_(r) is a non-zero value between −0.1 and 0.1.

This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims. 

What is claimed is:
 1. A heat pump system, comprising a hot side heat exchanger; a cold side heat exchanger; a pump operable to flow a working fluid between the hot and cold side heat exchangers; and a caloric heat pump comprising a regenerator housing extending along an axial direction between a first end portion of the regenerator housing and a second end portion of the regenerator housing, the regenerator housing defining a chamber that extends longitudinally along the axial direction between the first and second end portions of the regenerator housing, a plurality of stages positioned within the regenerator housing, the plurality of stages being arranged sequentially along the axial direction from the first end portion to the second end portion, each stage of the plurality of stages comprising a caloric material having a caloric temperature peak, the plurality of stages being arranged so that the caloric temperature peaks of the plurality of stages increase along the axial direction according to a predetermined, non-linear curve, and a field generator positioned adjacent to the plurality of stages to subject the plurality of stages to a variable field generated by the field generator.
 2. The heat pump system of claim 1, wherein the field generator comprises a magnet.
 3. The heat pump system of claim 1, wherein the field generator comprises an electromagnet.
 4. The heat pump system of claim 1, wherein the field generator, the plurality of stages, or both, are configured for cycling the plurality of stages in and out of the variable field during operation of the heat pump.
 5. The heat pump system of claim 1, wherein the field generator is axially fixed at a predetermined position relative to the first end portion and the second end portion.
 6. The heat pump system of claim 1, wherein each caloric material of the plurality of stages comprises a caloric temperature range, and wherein the caloric temperature ranges of the plurality of stages overlap between stages that are adjacent along the axial direction.
 7. The heat pump system of claim 1, wherein the predetermined, non-linear curve defines a curvature ratio between −0.5 and 0.5.
 8. The heat pump system of claim 7, wherein the predetermined, non-linear curve defines a curvature ratio between −0.1 and 0.1.
 9. The heat pump system of claim 1, wherein each stage of the plurality of stages defines a common axial length.
 10. The heat pump system of claim 1, wherein one or more stages of the plurality of stages defines a discrete axial length that is unique from an axial length defined by another stage of the plurality of stages.
 11. A refrigerator appliance, comprising: a cabinet defining a chilled chamber; and a heat pump system operable to cool the chilled chamber, the heat pump system comprising a cold side heat exchanger positioned at the chilled chamber; a hot side heat exchanger positioned outside the chilled chamber; a pump operable to flow a working fluid between the hot and cold side heat exchangers; and a caloric heat pump comprising: a regenerator housing extending along an axial direction between a first end portion of the regenerator housing and a second end portion of the regenerator housing, the regenerator housing defining a chamber that extends longitudinally along the axial direction between the first and second end portions of the regenerator housing, a plurality of stages positioned within the regenerator housing, the plurality of stages being arranged sequentially along the axial direction from the first end portion to the second end portion, each stage of the plurality of stages comprising a caloric material having a caloric temperature peak, the plurality of stages being arranged so that the caloric temperature peaks of the plurality of stages increase along the axial direction according to a predetermined, non-linear curve, and a field generator positioned adjacent to the plurality of stages to subject the plurality of stages to a variable field generated by the field generator.
 12. The refrigerator appliance of claim 11, wherein the field generator comprises a magnet.
 13. The refrigerator appliance of claim 11, wherein the field generator comprises an electromagnet.
 14. The refrigerator appliance of claim 11, wherein the field generator, the plurality of stages, or both, are configured for cycling the plurality of stages in and out of the variable field during operation of the heat pump.
 15. The refrigerator appliance of claim 11, wherein the field generator is axially fixed at a predetermined position relative to the first end portion and the second end portion.
 16. The refrigerator appliance of claim 11, wherein each caloric material of the plurality of stages comprises a caloric temperature range, and wherein the caloric temperature ranges of the plurality of stages overlap between stages that are adjacent along the axial direction.
 17. The refrigerator appliance of claim 11, wherein the predetermined, non-linear curve defines a curvature ratio between −0.5 and 0.5.
 18. The refrigerator appliance of claim 11, wherein the predetermined, non-linear curve defines a curvature ratio between −0.1 and 0.1.
 19. The refrigerator appliance of claim 11, wherein each stage of the plurality of stages defines a common axial length.
 20. The refrigerator appliance of claim 11, wherein one or more stages of the plurality of stages defines a discrete axial length that is unique from an axial length defined by another stage of the plurality of stages. 